PEO-b-P4VP摻混P4VP混合物之低臨界有序化現象研究

Self-assembly of PEO-b-P4VP and Its Blends with P4VP Homopolymer Displaying LCOT Behavior

許長正(Chang-Cheng Shiu)

指導教授 ： 陳信龍

國立清華大學/工學院/化學工程學系/碩士(2014年)

https://doi.org/10.6843/NTHU.2014.00229

摘要

利用變溫小角度X光散射，我們發現與探討了對稱的雙嵌段高分子聚氧乙烯-聚四乙烯吡啶(poly(ethylene oxide)-block-poly (4-vinylpyridine), PEO-b-P4VP)呈現有序-無序的相轉化(order-disorder transition, ODT)是低臨界有序化(Lower critical ordering transition, LCOT)的相行為，以及其與單嵌段高分子聚氧乙烯-聚四乙烯吡啶(Homopoly4VP, H4VP)所形成的混合物中，H4VP溶解進P4VP的行為。PEO-b-P4VP的ODT發生於降溫過程，當溫度接近相轉化溫度(TODT)時，大範圍有序的結構仍保持良好，這代表著傳統高臨界有序化(upper critical ordering transition, UCOT)相行為在ODT時所產生嚴重的熱擾動，於PEO-b-P4VP的LCOT中不再具有影響力，而此種LCOT是比較接近平均場理論的有序-無序相轉化行為。當H4VP與摻混進PEO-b-P4VP，PEO-b-P4VP仍呈現LCOT的相行為，且在微相分離的高溫下H4VP會溶解進入P4VP的微相中，在不同分子量的H4VP情況，形成濕型或乾型的溶解方式(wet-dry brush)，進而影響到其層狀的厚度，相較於典型的聚苯乙烯-聚異戊二烯(polystyrene-b-polyisoprene, PS-b-PI)，區分wet-dry brush的參數r (MH4VP/MB4VP)遠小於傳統上PS-b-PI所定義的1，這是由於在高溫的情況下，表面能和亂度同時扮演主導結構的角色，因此阻礙了H4VP均勻分散的企圖，為求不讓表面能過大，儘管摻混大量的H4VP使其4VP體積分率達到0.7，PEO-b-P4VP仍保持著層狀的結構。

關鍵字

低臨界有序-無序相轉化 ； 雙嵌段高分子摻混單嵌段高分子混合物 ； 乾-濕型溶解 ； 平均場理論

並列摘要

We have investigated the order-disorder transition (ODT) of a lamellae-forming PEO-b-P4VP exhibiting LCOT behavior and examined the solubilization behavior of P4VP homopolymer in its blends with the PEO-b-P4VP. PEO-b-P4VP exhibited ODT upon cooling. The temperature-dependent SAXS measurement revealed that as the TODT was approached on cooling, the long-range order of the lamellar structure was still well preserved, indicating that the thermal noise effect, which is prevalent in the conventional UCOT system, did not play a major role, such that the phase transition process may approach the mean-field behavior. When its blends with H4VP, which can be solubilized into the P4VP microdomains, also displayed LCOT behavior, where they showed a order-to-disorder transition (ODT) upon cooling. In the microphase-separated state, the interdomain distance D of the lamellae structure was found to increase with increasing molecular weight of H4VP (MH4VP) and the H4VP formed wet or dry brush solubilization. In contrast to the classical system of PS-b-PI / homopolymer blends, the critical value of r (MH4VP/MB4VP) below which the system shows completely wet brush behavior was found to lie significantly lower than 1.0. This phenomenon was attributed to the enhanced roles of both repulsive interaction energy and conformational entropy at high temperature, so as to hinder the uniform solubilization of H4VP. Even when the H4VP was uniformly solubilized in the P4VP microdomain, the lamellae morphology remained stable even when the overall P4VP composition was highly unsymmetric.

並列關鍵字

LCOT ； Mixtures of block polymer with homopolymer ； wet-dry brush ； mean-field theory

參考文獻

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